The hypothesis of this study is that Black asthmatic patients are less sensitive to B2-adrenergic receptor stimulation that White asthmatic patients. The specific aims of the propose study are to compare terbutaline concentration FEV1 response relationships, as a measure of plumonary B2-receptor sensitivity, and to compare terbutaline concentration-plasma potassium response relationships as a measure of extra-pulmonary B2-receptor sensitivity.